Devices for sensing yarn bobbin change are known. These known devices present a sensitive zone in which the connection portion between the yarn of one bobbin and the yarn of the next bobbin is housed.
Frequently, the connection portion is maintained within the sensitive zone by the use of yarn braking grippers, to prevent this portion from inadvertently escaping, to hence generate a false reading.
When the bobbin is approaching depletion, this connection portion is dragged towards the textile machine, hence leaving the sensitive zone. Suitable sensors, for example capacitive, optical or piezoelectric, sense this exit and indicate that the bobbin change, also known as “head-tail event”, has taken place.
Devices of the known type present however certain drawbacks.
Firstly, sensing the head-tail event is exclusively related to sensing the moment in which the yarn connection portion is dragged out of the sensitive zone of the device. Because of the high speed with which the yarn is fed to the textile machine, it can frequently happen that the device is unable to detect that single instantaneous event, and hence sense it.
Moreover, the frequent need to reposition the yarn braking grippers makes installation of such devices on textile machines substantially more complicated.
Again, the yarn braking grippers exert a braking action on the yarn which, at the moment of the head-tail event, must be counteracted and overcome, risking yarn breakage.